Suppressing Material Loss for Functional Nanophotonics Using Bandgap Engineering

TL;DR

This paper demonstrates how bandgap engineering of hydrogenated amorphous silicon nanoparticles suppresses material loss, enabling high-Q resonances in the visible range and tunable light scattering for nanophotonics applications.

Contribution

The study introduces hydrogenated amorphous silicon nanoparticles with bandgap engineering that achieve high-Q resonances in the visible spectrum, surpassing previous material loss limitations.

Findings

Achieved Q factors up to ~100 in visible and near-IR range.

Demonstrated ~70% reversible all-optical tuning of light scattering.

Enabled low-intensity all-optical tuning of nanoantennas.

Abstract

All-dielectric nanoantennas have recently opened exciting opportunities for functional nanophotonics, owing to their strong optical resonances along with low material loss in the near-infrared range. Pushing these concepts to the visible range is hindered by a larger absorption coefficient of Si and other high-index semiconductors, thus encouraging the search for alternative dielectrics for nanophotonics. In this paper, we employ bandgap engineering to synthesize hydrogenated amorphous Si nanoparticles (a-Si:H NPs) offering ideal features for functional nanophotonics. We observe significant material loss suppression in a-Si:H NPs in the visible range caused by hydrogenation-induced bandgap renormalization, producing resonant modes in single a-Si:H NPs with Q factors up to ~100, in the visible and near-IR range for the first time. In order to demonstrate light-matter interaction enhancement, we realize highly tunable all-dielectric nanoantennas coupling them to photochromic spiropyran (SP) molecules. We show ~70% reversible all-optical tuning of light scattering at the high-Q resonant mode, along with minor tunability when out of resonance. This remarkable all-optical tuning effect is achieved under a low incident light intensity ~3.8 W/cm2 for UV light and ~1.1*10^2 W/cm2 for green light.